RE: [PATCH 1/2] Fix reverse stepping multiple contiguous PC ranges over the line table.

[Carl Love via Gdb-patches <gdb-patches@sourceware.org>]

On Fri, 2023-06-23 at 13:44 -0400, Simon Marchi wrote:
> 
> On 6/22/23 12:52, Carl Love wrote:
> > Simon:
> > 
> > On Mon, 2023-06-19 at 13:11 -0400, Simon Marchi wrote:
> > > > --- a/gdb/testsuite/lib/gdb.exp
> > > > +++ b/gdb/testsuite/lib/gdb.exp
> > > > @@ -4794,6 +4794,8 @@ proc quote_for_host { args } {
> > > >   #     debug information
> > > >   #   - text_segment=addr: Tell the linker to place the text
> > > > segment at ADDR.
> > > >   #   - build-id: Ensure the final binary includes a build-id.
> > > > +#   - no-column-info: Disable generation of column table
> > > > information.
> > > > +#   - column-info: Enable generation of column table
> > > > information.
> > > >   #
> > > >   # And here are some of the not too obscure options understood
> > > > by
> > > > DejaGnu that
> > > >   # influence the compilation:
> > > > @@ -5003,6 +5005,34 @@ proc gdb_compile {source dest type
> > > > options}
> > > > {
> > > >               } else {
> > > >                   error "Don't know how to handle text_segment
> > > > option."
> > > >               }
> > > > +     } elseif { $opt == "column-info" } {
> > > > +         if {[test_compiler_info {gcc-*}]} {
> > > > +             if {[test_compiler_info {gcc-[1-6]-*}]} {
> > > > +                 error "gdb_compile option no-column-info not
> > > > supported."
> > > 
> > > I think this path should return the equivalent of "failed to
> > > compile",
> > > instead of throwing an error.  Control will go back to the test,
> > > which
> > > will generally skip the portion of the test that requires that
> > > binary.
> > 
> > Not entirely sure how to accomplish what you are looking for.
> > 
> > I change:
> >   error "gdb_compile option no-column-info not supported."
> > to
> >   set result "option no-column-info not supported."
> >   clone_output "gdb compile failed, $result"
> >   return 1
> > 
> > When I force the if {[test_compiler_info...]} tp be true to test
> > this,
> > I get:
> > 
> >    get_compiler_info: gcc-12-2-1
> >    gdb compile failed, option no-column-info not supported.
> >    UNTESTED: gdb.reverse/func-map-to-same-line.exp:
> >    with_column_info=yes: failed t\
> >    o prepare
> >    testcase /home/carll/GDB/build-reverse-multiple-
> >    contiguous/gdb/testsuite/../../\
> >    ../binutils-gdb-reverse-multiple-
> >    contiguous/gdb/testsuite/gdb.reverse/func-map-\
> >    to-same-line.exp completed in 0 seconds
> > 
> >                    === gdb Summary ===
> > 
> >    # of untested testcases         1
> > 
> > The test case doesn't have any part of the test that doesn't
> > require
> > compiling so it is not clear if that would work with this
> > fix.  Anyway,
> > wanted to run that by you to see if this is an appropriate fix?  I
> > am
> > really not sure about it.  Thanks.
> 
> I think that's the expected behavior.  The UNTESTED is emitted by
> build_executable_from_specs, I think.  If the test used gdb_compile,
> I
> think we wouldn't see an UNTESTED.  But as far as your addition is
> concerned, I think it's fine.
> 
> I just thought of a simpler alternative though.  Just remove the
> version
> check.  If we build with an older gcc, there will simply be a message
> that says that the flag is not recognized, and the result should be
> just
> the same.  I just hacked it locally and changed the flag name to be
> wrong (I don't have a gcc <= 6 on hand to test).  It looks like:

Yea, hacking the if {[test_compiler_info {gcc-[...]}  is how I have
been testing it as well.  :-)
> 
>     Executing on host: gcc  -fno-stack-protector  -fdiagnostics-
> color=never -gcolumn-info-foo -c -g  -o /home/simark/build/binutils-
> gdb/gdb/testsuite/outputs/gdb.reverse/func-map-to-same-line/func-map-
> to-same-line0.o /home/simark/src/binutils-
> gdb/gdb/testsuite/gdb.reverse/func-map-to-same-line.c    (timeout =
> 300)
>     builtin_spawn -ignore SIGHUP gcc -fno-stack-protector
> -fdiagnostics-color=never -gcolumn-info-foo -c -g -o
> /home/simark/build/binutils-
> gdb/gdb/testsuite/outputs/gdb.reverse/func-map-to-same-line/func-map-
> to-same-line0.o /home/simark/src/binutils-
> gdb/gdb/testsuite/gdb.reverse/func-map-to-same-line.c
> 
>     gcc: error: unrecognized debug output level 'column-info-foo'
> 
>     compiler exited with status 1
>     output is:
>     gcc: error: unrecognized debug output level 'column-info-foo'
> 
> 
>     gdb compile failed, gcc: error: unrecognized debug output level
> 'column-info-foo'
>     UNTESTED: gdb.reverse/func-map-to-same-line.exp:
> with_column_info=yes: failed to prepare

Yes, that seems to give us the desired result.
> 
> I then thought about the "no-column-info" case.  Currently, you error
> out for gccs <= 6.  However, shouldn't we just compile without any
> special flag in that case, since there just wasn't any support for
> column-info back then?

OK, but seems like we should also warn the user that the option is not
supported and we are ignoring it.  I put 

         # In this case, don't add the compile line option and       
         # the result will be the same as using no-column-info       
         # on a version that supports the option.                    
         warning "gdb_compile option no-column-info not supported, ignoring."

in for this case.

                               Carl